Stem cells are a generic term for undifferentiated cells before differentiated stages, which can be obtained from various tissues. Stem cells have properties capable of continuously producing cells identical to themselves for a certain amount of time in an undifferentiated state, and properties capable of differentiating into various cells which constitute biological tissues, under proper conditions.
Stem cells can be broadly classified as embryonic stem cells and adult stem cells, according to differentiation potency and generating stage. As another classification according to differentiation potency of stem cells, stem cells can be divided into pluripotent, multipotent, and unipotent stem cells.
Adult stem cells can be classified as multipotent or unipotent stem cells. As representative adult stem cells, there are mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs). It is known that mesenchymal stem cells differentiate into chondrocytes, osteoblasts, adipocytes, myocytes, and neurons, and that hematopoietic stem cells mainly differentiate into blood cells in blood, such as erythrocytes, leukocytes, or platelets.
Meanwhile, pluripotent stem cells refer to stem cells with multipotency which can differentiate into all three germ layers constituting the body, thereby capable of differentiating into every cell or organ tissue of human bodies. Generally, embryonic stem cells correspond thereto. Human embryonic stem cells raise many ethical concerns, because they are created from embryos that may develop into human beings. However, embryonic stem cells are known as having excellent cell proliferation and differentiation potency, compared with adult stem cells. Adult stem cells cause less ethical issues, because they can be obtained from bone marrow, blood, brain, skin, and the like. However, adult stem cells have limited differentiation potency, compared with embryonic stem cells.
As a solution for overcoming these problems, various techniques have been attempted to produce customized pluripotent stem cells similar to embryonic stem cells by dedifferentiating cells derived from adult stem cells. Representative techniques include fusion with ES cell, somatic cell nuclear transfer, reprogramming by gene factor, and the like. According to fusion with ES cell, induced cells have two further pairs of genes, and this causes a problem in terms of stability of cells. Somatic cell nuclear transfer requires a large number of ovums and has very low efficiency, which are disadvantages. Reprogramming by gene factor is a technique of using viruses including oncogenes by inserting specific genes, to induce dedifferentiation, and this technique has a high risk of cancer occurrence and is disadvantageous in possibility of development of cell therapy products due to low efficiency and difficulty in terms of methods.
In order to obtain pluripotent stem cells successfully and abundantly, medium compositions in the stage of culturing isolated umbilical cord-derived mononuclear cells is very important. Thus, there is a demand for studies for preparing pluripotent stem cells with a much more amount and in a higher efficient induction method.
The matters provided in the above background art are only intended to help better understand the background of the present invention. It should not be construed, however, that the present invention falls under the related art already known to a person skilled in the art.